WO2007010801A1

WO2007010801A1 - Step-up/down switching regulator, its control circuit, and electronic apparatus using same

Info

Publication number: WO2007010801A1
Application number: PCT/JP2006/313881
Authority: WO
Inventors: Shinya Karasawa
Original assignee: Rohm Co., Ltd.
Priority date: 2005-07-15
Filing date: 2006-07-12
Publication date: 2007-01-25
Also published as: TW200705788A; JP2007028784A; CN101218734A; US20090122585A1; JP4652918B2

Abstract

A switching regulator of synchronous rectifying type capable of blocking the current flowing when voltage step-up/down operation is stopped without providing any DC current preventive transistor. An input voltage Vin is supplied to a first terminal (102) of a control circuit (100) through an inductor (L1) connected to the outside. An output capacitor (Co) is connected to a second terminal (104). A switching transistor (SW1) is disposed between the first terminal (102) and the ground, and a synchronous rectifying transistor (SW2) is disposed between the first and second terminals (102, 104). A first transistor (M1) is disposed between the back gate of a synchronous rectifying transistor (M2) and the first terminal (102), and the second transistor (M2) is disposed between the back gate and the second terminal (104). A switching control section (12) keeps the first and second transistors (M1, M2) off during a step-up stop period and keeps the first transistor (M1) off and the second transistor (M2) on during a step-up period.

Description

Specification

Step-up and step-down switching regulators, their control circuits, and electronic equipment using them

Technical field

TECHNICAL FIELD [0001] The present invention relates to a switching regulator, and more particularly to a synchronous rectification step-up or step-down switching regulator.

Background art

[0002] In recent years, various electronic devices such as mobile phones, PDAs (Personal Digital Assistants), and notebook personal computers have a light emitting diode (hereinafter referred to as an LED), a microprocessor, or a microprocessor, Many other devices that operate with different power supply voltages such as analog and digital circuits are installed.

On the other hand, batteries such as lithium ion batteries are mounted as power sources in such electronic devices. A DCZDC converter such as a switching regulator that boosts or lowers the battery voltage is used to supply the voltage output from the lithium-ion battery to devices operating at different power supply voltages.

[0004] A step-up or step-down switching regulator includes a method using a rectifying diode (hereinafter referred to as a diode rectification method) and a method using a synchronous rectification transistor instead of a diode (hereinafter referred to as synchronous rectification). Method). In the former case, a diode is required in addition to the inductor and output capacitor outside the force control circuit, which has the advantage that high efficiency can be obtained when the load current flowing through the load is small, so that the circuit area increases. In the latter case, the efficiency when the current supplied to the load is small is inferior to the former. However, since a transistor is used instead of a diode, it can be integrated inside the LSI, and the circuit area including peripheral components As a result, downsizing is possible. In electronic devices that require miniaturization such as cellular phones, switching regulators using rectifying transistors (hereinafter referred to as synchronous rectification switching regulators) are often used.

[0005] Here, the synchronous rectification step-up switching regulator is supplied with a battery voltage or the like. A synchronous rectification transistor and an inductor are connected in series between the input terminal connected to the output terminal that outputs the boosted voltage (hereinafter referred to as output voltage). When a P-channel MOSFET is used for the synchronous rectification transistor and its back gate is connected to the source (or drain), even when the boost operation is stopped by turning off the synchronous rectification transistor, The problem was that current would flow to the load via the body diode (parasitic diode) between the drain (or source) and the inductor.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-32875

Patent Document 2: JP 2002-252971 A

Disclosure of the invention

Problems to be solved by the invention

In order to cut off the current flowing to the load via the synchronous rectification transistor and the inductor when the boosting operation is stopped, a method of providing a DC prevention transistor as a switch element on the current path is conceivable. However, this DC prevention transistor acts as a resistance element during the boosting operation, resulting in power loss. In order to reduce the power loss due to the DC prevention transistor, it is necessary to increase the transistor size and reduce the on-resistance. However, this causes a problem that the circuit area increases.

[0008] The present invention has been made in view of an energetic problem, and its comprehensive purpose is to perform synchronous rectification switching that can cut off the current that flows when the step-up / step-down operation is stopped without providing a DC prevention transistor. It is in the provision of the Regulator.

Means for solving the problem

[0009] One embodiment of the present invention relates to a control circuit for a synchronous rectification step-up switching regulator. This control circuit includes a first terminal to which an input voltage is supplied via an externally connected inductor, a second terminal to which an output capacitor is connected, a switching transistor provided between the first terminal and the ground, A synchronous rectification transistor provided between the first terminal and the second terminal; a back gate of the synchronous rectification transistor; a first transistor provided between the first terminal; a back gate of the synchronous rectification transistor; A second transistor provided between the two terminals; and a switch control unit that controls on / off of the first and second transistors. [0010] According to this aspect, instead of connecting the back gate of the synchronous rectification transistor to the source or the drain, the first and second transistors are provided, and the on / off of the two transistors is controlled, whereby the synchronous rectification transistor The current flowing through the back gate can be controlled. As a result, even if a DC prevention transistor is not provided in series with the inductor, it is possible to prevent unnecessary current from flowing and preventing voltage from appearing at the output terminal when boosting is stopped.

The switch control unit turns off the first transistor and the second transistor during the boost stop period of the boost switching regulator driven by the present control circuit, and turns off the first transistor during the boost operation period. Two transistors may be turned on.

By turning off both the first transistor and the second transistor during the boost stop period, the current path through the back gate of the synchronous rectification transistor can be cut off. Further, during the boosting operation period, a current path can be generated via the back gate of the synchronous rectification transistor by turning on the second transistor.

[0012] The switch control unit may gradually turn on the second transistor while the first transistor is turned on during the start-up period during which the step-up switching regulator enters the operation stop state force step-up operation state. .

In this case, the synchronous rectification transistor can be prevented from being latched up.

Another aspect of the present invention relates to a control circuit for a synchronous rectification step-down switching regulator. This control circuit includes a first terminal that outputs a switching voltage to an externally connected inductor, a second terminal that is supplied with an input voltage from the outside, and a switching transistor provided between the first terminal and the second terminal. A synchronous rectifying transistor provided between the first terminal and the ground, a first transistor provided between the back gate and the first terminal of the switching transistor, and provided between the back gate of the switching transistor and the second terminal. And a switch controller for controlling on / off of the first and second transistors.

[0014] According to this aspect, instead of connecting the back gate of the switching transistor to the drain or the source, the first and second transistors are provided, and the on / off of the two transistors is controlled, so that the switching transistor is connected via the back gate of the switching transistor. The current flowing through be able to.

The switch control unit turns off the first transistor and the second transistor during the step-down stop period of the step-down switching regulator driven by the present control circuit, turns off the first transistor during the step-down operation period, Two transistors may be turned on.

By turning off both the first transistor and the second transistor during the step-down stop period, the current path through the knock gate of the switching transistor can be cut off. Also, during the step-down operation period, a current path through the back gate of the switching transistor can be generated by turning on the second transistor.

[0016] The switch control unit may gradually turn on the second transistor while the first transistor is turned off during the start-up period in which the step-down switching regulator transitions from the operation stop state to the step-down operation state. .

[0017] Yet another embodiment of the present invention relates to a switching regulator control circuit capable of switching between a step-up mode and a step-down mode. This control circuit functions as a switching transistor in the boost mode, functions as a synchronous rectification transistor in the step-down mode, and functions as a synchronous rectification transistor in the step-up mode. Sometimes a second switching transistor that functions as a switching transistor, a first transistor provided between the back gate and drain of the second switching transistor, and a second transistor provided between the knock gate and source of the second switching transistor. A transistor and a switch control unit for controlling on / off of the first and second transistors.

[0018] According to this aspect, the switch control unit can appropriately switch the on / off states of the first and second transistors in the step-up mode and the step-down mode.

[0019] The switching transistor, the synchronous rectification transistor, the first transistor, the second transistor, and the switch control unit may be integrated on a single semiconductor substrate. The integration here includes the case where all the circuit components are formed on a semiconductor substrate and the case where the main components of the circuit are integrated as a single unit. Some resistors and capacitors are provided outside the semiconductor substrate.

[0020] Another aspect of the present invention is a step-up switching regulator. This switching level The regulator includes the control circuit described above, one end connected to the first terminal of the control circuit, the other end to which the input voltage is applied, one end connected to the second terminal of the control circuit, and the other end grounded. And output a voltage at one end of the output capacitor.

[0021] According to this aspect, by appropriately controlling on / off of the first and second transistors by the switch control unit, the current flowing through the back gate of the synchronous rectification transistor can be controlled, and the boost is stopped. Sometimes, an input voltage appears at one end of the output capacitor or current can be prevented from flowing through the load.

[0022] Another aspect of the present invention is a step-down switching regulator. The switching regulator includes an output capacitor having one end grounded, an inductor having one end connected to the other end of the output capacitor, and the above-described control circuit that supplies a switching voltage to the other end of the inductor. The voltage at the other end of the output capacitor is output.

According to this aspect, the current flowing through the back gate of the switching transistor can be controlled by controlling on / off of the first and second transistors.

[0024] Yet another embodiment of the present invention is an electronic device. This electronic device includes a battery and the above-described switching regulator that increases or decreases the voltage of the battery.

According to this embodiment, inrush current at power-on can be suppressed by controlling the current flowing through the synchronous rectification transistor or the back gate of the switching transistor. In addition, since there is no need to provide a DC prevention transistor, loss due to resistance can be reduced, and the circuit area can be reduced.

[0025] It should be noted that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention that are mutually replaced between methods, devices, systems, etc. are also effective as an aspect of the present invention. Brief Description of Drawings

FIG. 1 is a circuit diagram showing a configuration of a step-up switching regulator according to a first embodiment.

2 is a time chart showing an operating state of the step-up switching regulator of FIG.

FIG. 3 is a circuit diagram showing a configuration of a step-up switching regulator according to a second embodiment.

4 is a time chart showing an operating state of the step-down switching regulator of FIG. 3. FIG. 5 is a circuit diagram showing a configuration of a control circuit according to a third embodiment.

FIG. 6 is a block diagram showing a configuration of an electronic device in which the control circuit of FIGS. 1, 3, and 5 is preferably used.

Explanation of symbols

[0027] 100 control circuit, 102 1st terminal, 104 2nd terminal, 106 voltage feedback terminal, 11 0 control circuit, 112 1st terminal, 114 2nd terminal, 116 voltage feedback terminal, 120 control circuit, 122 1st control circuit Terminal, 124 second terminal, 126 voltage feedback terminal, 128 voltage feedback terminal, 200 step-up switching regulator, 202 input terminal, 204 output terminal, 210 step-down switching regulator, 212 input terminal, 214 output terminal ,

SW1 switching transistor, SW2 synchronous rectification transistor, SW3 switching transistor, SW4 synchronous rectification transistor, SW5 first switching transistor, SW6 second switching transistor, Ml first transistor, M2 second transistor, 10 driver circuit, 12 Switch control unit, 14 pulse width modulator, L1 inductor, Co output capacitor, Vgl first gate control signal, Vg2 second gate control signal, D1 first body diode, D2 second body diode, Vcntl first control Signal, Vcnt2 Second control signal.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described based on a preferred embodiment with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations described in the embodiments are not necessarily essential to the invention.

[0029] (First embodiment)

The first embodiment of the present invention relates to a synchronous rectification step-up switching regulator. FIG. 1 is a circuit diagram showing a configuration of a step-up switching regulator 200 according to the first embodiment. The step-up switching regulator 200 is a synchronous rectification switching regulator including a control circuit 100, an inductor Ll, and an output capacitor Co. An input voltage Vin is applied to the input terminal 202. The step-up switching regulator 200 according to the present embodiment steps up the input voltage Vin at a predetermined step-up ratio and outputs the output voltage Vout from the output terminal 204.

An inductor L1 is connected between the first terminal 102 of the control circuit 100 and the input terminal 202 of the step-up switching regulator 200. The input voltage Vin is supplied to the first terminal 102 via the inductor L1. An output capacitor Co is connected between the second terminal 104 and the ground.

[0031] The control circuit 100 includes a switching transistor SW1, a synchronous rectification transistor SW2, a first transistor Ml, a second transistor M2, a driver circuit 10, a switch control unit 12, and a pulse width modulator 14, on one semiconductor substrate. Are collected.

The switching transistor SW1 is an N-channel MOSFET, the drain is connected to the first terminal 102, and the source is grounded. The synchronous rectification transistor SW2 is a P-channel MOSFET, and has a drain connected to the first terminal 102 and a source connected to the second terminal 104. The first gate control signal Vgl and the second gate control signal Vg2 output from the driver circuit 10 are input to the gates of the switching transistor SW1 and the synchronous rectification transistor SW2.

The output voltage Vout of the step-up switching regulator 200 is fed back to the voltage feedback terminal 106 of the control circuit 100. The output voltage Vout fed back is input to the pulse width modulator 14. The pulse width modulator 14 generates a pulse width modulation signal (hereinafter referred to as a PWM signal Vpwm) in which the ratio between the high level and the low level time, that is, the duty ratio changes. The duty ratio of the PWM signal Vpwm is controlled so that the output voltage Vout approaches a predetermined reference voltage.

[0034] The driver circuit 10 generates the first gate control signal Vgl and the second gate control signal Vg2 based on the PWM signal Vpwm output from the pulse width modulator 14, and the switching transistor SW1 and the Output to the gate of the rectifying transistor SW2. The switching transistor SW1 and the synchronous rectification transistor SW2 are alternately turned on and off based on the duty ratio of the PWM signal Vpwm.

[0035] As shown in FIG. 1, body diodes (parasitic diodes) Dl and D2 exist between the back gate and the drain of the synchronous rectification transistor SW2 or between the back gate and the source. The Hereinafter, these are referred to as a first body diode Dl and a second body diode D2. Normally, the back gate of this P-channel MOSFET is used connected to the source, so that both ends of the second body diode D2 are used in a short-circuited state. In this case, as described above, the current flows from the input terminal 202 to the output terminal 204 via the first body diode D1 when the boosting is stopped.

On the other hand, in the control circuit 100 according to the present embodiment, instead of connecting the back gate of the synchronous rectification transistor SW2 to the source, a first transistor Ml and a second transistor M2 are provided.

The first transistor Ml is a P-channel MOSFET, and is provided between the knock gate of the switching transistor SW 1 and the first terminal 102. That is, the source of the first transistor Ml is connected to the first terminal 102, and the drain is connected to the back gate of the synchronous rectification transistor SW2. The second transistor M2 is also a P-channel MOSFET, and is provided between the knock gate of the switching transistor SW1 and the second terminal 104. That is, the source of the second transistor M2 is connected to the back gate of the synchronous rectification transistor SW2, and the drain is connected to the second terminal 104.

[0037] The switch control unit 12 generates the first control signal Vcntl and the second control signal Vcnt2 according to the operating state of the step-up switching regulator 200, and the gates of the first transistor Ml and the second transistor M2 Each voltage is controlled by controlling the voltage. In the present embodiment, the step-up switching regulator 200 is in a step-up stop state in which the step-up operation is stopped and power supply to the load is stopped, and a step-up operation state in which a predetermined output voltage Vout is supplied to the load by the step-up operation. And the start-up state corresponding to the transition period from the boost stop state to the boost operation state.

[0038] The operation of the step-up switching regulator 200 configured as described above will be described. FIG. 2 is a time chart showing the operating state of the step-up switching regulator 200. In the figure, the vertical axis and the horizontal axis are enlarged or reduced as appropriate for the sake of brevity.

[0039] Prior to time TO, the step-up switching regulator 200 is in a step-up stop state. At this time, the switch control unit 12 sets the first control signal Vcntl and the second control signal Vcnt2 to high level. Then, both the first transistor Ml and the second transistor M2 are turned off. When both the first transistor M1 and the second transistor M2 are turned off, no current flows through the first body diode Dl and the second body diode D2 of the synchronous rectification transistor SW2. As a result, the current path via the back gate of the synchronous rectification transistor SW2 can be interrupted between the input terminal 202 and the output terminal 204, current flows through the load, or the output terminal 204 is close to the input voltage Vin. The voltage can be prevented from appearing. Before time TO, the potential Vbg of the back gate of the synchronous rectification transistor SW2 becomes high! /.

[0040] At time TO, a standby signal STB (not shown in FIG. 1) changes from a low level to a high level, and activation of the step-up switching regulator 200 is instructed. When the standby signal STB becomes high level, the switch control unit 12 sets the first control signal Vcntl to low level and turns on the first transistor Ml. Further, the switch control unit 12 gradually decreases the second control signal Vcnt2 from the high level to the low level. Thereafter, when the second control signal Vcnt2 decreases and the gate-source voltage of the second transistor M2 becomes higher than the threshold voltage V, the second transistor M2 is turned on. As the second transistor M2 is gradually turned on, the output voltage Vout appearing at the second terminal 104 rises to near the input voltage Vin applied to the input terminal 202.

As described above, the step-up switching regulator 200 according to the present embodiment can suppress the occurrence of the inrush current by gradually turning on the second transistor M2 at the time of startup. Monkey.

[0042] When the start-up is completed at time T2, the switch control unit 12 sets the first control signal Vcntl to high level and turns off the first transistor Ml. Thereafter, at time T3, the switching operation of the switching transistor SW1 and the synchronous rectification transistor SW2 is started by the pulse width modulator 14 and the driver circuit 10. When the boost operation is started at time T3, the output voltage Vout rises to a predetermined reference voltage.

In the step-up switching regulator 200 according to the present embodiment, the first transistor Ml is turned off and the second transistor M2 is turned on during the step-up operation. Since this is a circuit state similar to the state in which the back gate of the P-channel MOSFET is connected to the source, the boosting operation can be suitably performed. In addition, starting at time TO and the force By starting the boosting operation at time T3 after the lapse of the period, the back gate voltage Vbg of the switching transistor SW1 decreases! /, While the switching transistor SW1 is turned on and latch-up occurs. Can be prevented.

[0043] (Second embodiment)

The second embodiment relates to a synchronous rectification step-down switching regulator 210. FIG. 3 is a circuit diagram showing a configuration of the step-down switching regulator 210 according to the second embodiment. The step-down switching regulator 210 is a synchronous rectification switching regulator including a control circuit 110, an inductor Ll, and an output capacitor Co. In this figure, the same or equivalent components as those in FIG.

An input voltage Vin is applied to the input terminal 212. The step-down switching regulator 210 according to the present embodiment steps down the input voltage Vin and outputs the output voltage Vout from the output terminal 214. An inductor L1 is connected between the first terminal 112 of the control circuit 110 and the output terminal 214 of the step-down switching regulator 210. An output capacitor Co is connected between the output terminal 214 and the ground. The first terminal 112 outputs the switching voltage Vsw to the inductor L 1 connected to the outside. An input voltage Vin is supplied to the second terminal 114 from the outside.

The control circuit 110 includes a switching transistor SW3, a synchronous rectification transistor SW4, a first transistor Ml, a second transistor M2, a driver circuit 10, a switch control unit 12, and a pulse width modulator 14.

The synchronous rectification transistor SW4 is an N-channel MOSFET, and has a drain connected to the first terminal 112 and a source grounded. The switching transistor SW3 is a P-channel MOSFET, and has a drain connected to the first terminal 112 and a source connected to the second terminal 114. The first gate control signal Vg3 and the second gate control signal Vg4 output from the driver circuit 10 are input to the gates of the switching transistor SW3 and the synchronous rectification transistor SW4.

The output voltage Vout of the step-down switching regulator 210 is fed back to the voltage feedback terminal 116 of the control circuit 110. The feedback output voltage Vout is the pulse width modulator 14 Is input. The pulse width modulator 14 and the driver circuit 10 drive the switching transistor SW3 and the synchronous rectification transistor SW4 based on the feedback output voltage Vout.

[0048] In the control circuit 110 according to the present embodiment, instead of connecting the back gate of the switching transistor SW3 to the source, a first transistor Ml and a second transistor M2 are provided.

The first transistor Ml is a P-channel MOSFET, and is provided between the knock gate of the switching transistor SW 3 and the first terminal 112. That is, the source of the first transistor Ml is connected to the first terminal 112, and the drain is connected to the back gate of the switching transistor SW3.

The second transistor M2 is also a P-channel MOSFET, and is provided between the knock gate of the switching transistor SW3 and the second terminal 114. That is, the source of the second transistor M2 is connected to the back gate of the switching transistor SW3, and the drain is connected to the second terminal 114.

[0049] The switch control unit 12 generates the first control signal Vcntl and the second control signal Vcnt2 according to the operating state of the step-down switching regulator 210, and the gates of the first transistor Ml and the second transistor M2 Each voltage is controlled by controlling the voltage. In the present embodiment, the step-down switching regulator 210 is a step-down stop state in which the step-down operation is stopped to stop power supply to the load, and a step-down operation state in which a predetermined output voltage Vout is supplied to the load by the step-down operation. , And the start-up state corresponding to the transition period from the step-down stop state to the step-down operation state.

[0050] The operation of the step-down switching regulator 210 configured as described above will be described. FIG. 4 is a time chart showing the operating state of the step-down switching regulator 210. In the figure, the vertical axis and the horizontal axis are enlarged or reduced as appropriate for the sake of brevity.

Prior to time TO, the step-down switching regulator 210 is in a step-down stop state. At this time, the switch control unit 12 sets the first control signal Vcntl and the second control signal Vcnt2 to high level to turn off both the first transistor Ml and the second transistor M2. 1st transistor M When both the first and second transistors M2 are turned off, no current flows through the first body diode Dl and the second body diode D2 of the switching transistor SW3. Before the time TO, the potential Vbg of the back gate of the synchronous rectification transistor SW2 is high.

At time TO, a standby signal STB (not shown in FIG. 3) changes from a low level to a high level, and the start of the step-down operation of step-down switching regulator 210 is instructed. When the standby signal STB becomes high level, the switch control unit 12 gradually decreases the second control signal Vcnt2 from high level to low level while maintaining the first control signal Vcntl at the neutral level. At this time, the back gate voltage Vbg of the switching transistor SW3 is maintained at a high level.

As described above, the step-down switching regulator 210 according to the present embodiment causes the input voltage Vin to appear in the switching voltage Vsw by turning off the first transistor Ml at the time of startup. Can be prevented.

[0054] Startup is completed at time T1. After that, at time T2, the switching operation of the switching transistor SW3 and the synchronous rectification transistor SW4 is started by the pulse width modulator 14 and the driver circuit 10. When step-down operation is started at time T2, the output voltage Vout rises to the specified reference voltage Vref.

In the step-down switching regulator 210 according to the present embodiment, the first transistor Ml is off and the second transistor M2 is on during the step-down operation. Since this is a circuit state similar to the state in which the back gate of the P-channel MOSFET is connected to the source, the step-down operation can be suitably performed.

[0055] (Third embodiment)

The control circuit 100 shown in FIG. 1 and the control circuit 110 shown in FIG. 3 have the same circuit configuration, and the arrangement of the external inductor Ll, output capacitor Co, input voltage Vin, and output voltage Vout appear. The position is different. Therefore, in the third embodiment, the control circuit 100 in FIG. 1 and the control circuit 110 in FIG. 3 are used as a control circuit for a switching regulator capable of switching between a step-up type and a step-down type.

FIG. 5 is a circuit diagram showing a configuration of the control circuit 120 according to the third embodiment. control The circuit 120 includes a first switching transistor SW5, a second switching transistor SW6, a first transistor Ml, a second transistor M2, a driver circuit 10, a switch control unit 12, and a noise width modulator 14. The first switching transistor SW5 functions as a switching transistor in the step-up mode, and functions as a synchronous rectification transistor in the step-down mode. The second switching transistor SW6 functions as a synchronous rectification transistor in the step-up mode, and functions as a switching transistor in the step-down mode. The first transistor Ml and the second transistor M2 are both P-channel MOS FETs. The output voltage is fed back to the voltage feedback terminal 126. The first terminal 122 corresponds to the first terminal 102 in FIG. 1 or the first terminal 112 in FIG. 3, and the second terminal 124 corresponds to the second terminal 104 in FIG. 1 or the second terminal 114 in FIG.

[0057] The first transistor Ml is provided between the back gate and the drain of the second switching transistor SW6. The second transistor M2 is provided between the back gate and the source of the second switching transistor.

A mode instruction signal MODE for designating the step-up mode or the step-down mode is input to the mode terminal 128. The mode instruction signal MODE is input to the switch control unit 12. The switch control unit 12 determines whether to operate in the step-up mode or the step-down mode based on the mode instruction signal MODE, and controls on / off of the first transistor Ml and the second transistor M2 based on the determination result. . The switch control unit 12 controls the first transistor Ml and the second transistor M2 by the method described in the first embodiment in the step-up mode, and the second embodiment in the step-down mode. The first transistor Ml and the second transistor M2 are controlled by the method described in the embodiment.

[0059] According to the control circuit 120 configured as described above, even when the user uses the control circuit as either a step-up switching regulator or a step-down switching regulator, the first transistor Ml, The second transistor M2 can be controlled.

FIG. 6 is a block diagram showing a configuration of an electronic device 300 in which the control circuits 100, 110, 120 of FIGS. 1, 3, and 5 are preferably used. The electronic device 300 is, for example, a digital still camera or a mobile phone terminal, and includes a battery 310, a power supply device 320, an analog circuit 330, a digital circuit 340, a microcomputer 350, and an LED 360. The battery 310 is, for example, a lithium ion battery, and outputs about 3 to 4 V as the battery voltage Vbat. The analog circuit 330 includes a circuit block that stably operates at a power supply voltage Vcc = 3.4V. The digital circuit 340 includes various DSPs (Digital Signal Processors) and the like, and includes a circuit block that stably operates at a power supply voltage Vdd = 3.4V. The microcomputer 350 is a block that comprehensively controls the entire electronic device 300, and operates at a power supply voltage of 1.5V. 1 ^: 0360 includes 1 ^} 83 (1 ^: 0) (31 ^ Emitting Diode) of 1¾}, and is used as a liquid crystal knock light or lighting. A drive voltage of 4V or more is required for driving. .

[0061] The power supply device 320 is a multi-channel switching power supply, and includes a switching regulator for stepping down or stepping up the battery voltage Vbat as necessary for each channel. The analog circuit 330, the digital circuit Supply appropriate power supply voltage to 340, microcomputer 350, and LED360.

The control circuit 120 of FIG. 5 according to the present embodiment can be suitably used for such a power supply device 320 by arranging a plurality of control circuits 120 in parallel to constitute a multi-channel control circuit. That is, when a 4-channel control circuit is configured, the third channel CH3 that supplies the power supply voltage to the microcomputer 350 is operated in the step-down mode, and the fourth channel CH4 that supplies the power supply voltage to the LED 360 is in the step-up mode. Just make it work!

[0062] The above embodiment is merely an example, and it is understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. It is where it is done.

In the embodiment, the case where the control circuit 100 or the like is integrated in one LSI has been described. However, the present invention is not limited to this, and some components are discretely provided outside the LSI. It may be provided as a chip element or chip component, or may be composed of multiple LSIs.

[0064] In the present embodiment, the setting of the logic values of the high level and the low level is merely an example, and can be freely changed by appropriately inverting it with an inverter or the like.

[0065] Although the present invention has been described based on the embodiment, the embodiment describes the principle and application of the present invention. Needless to say, in the embodiment, many modifications and arrangements can be made without departing from the spirit of the present invention defined in the claims. It ’s ugly! /.

Industrial applicability

The control circuit of the switching regulator according to the present invention can be used for a power supply device.

Claims

The scope of the claims

[1] A control circuit for a synchronous rectification step-up switching regulator,

A first terminal to which an input voltage is supplied via an externally connected inductor, a second terminal to which an output capacitor is connected,

A switching transistor provided between the first terminal and the ground;

A synchronous rectification transistor provided between the first terminal and the second terminal; a first transistor provided between a back gate of the synchronous rectification transistor and the first terminal;

A second transistor provided between a back gate of the synchronous rectification transistor and the second terminal;

A switch controller for controlling on / off of the first and second transistors;

A control circuit comprising:

[2] The switch control unit turns off the first transistor and the second transistor during the boost stop period of the boost switching regulator driven by the control circuit, and the first controller during the boost operation period. 2. The control circuit according to claim 1, wherein one transistor is turned off and the second transistor is turned on.

[3] The switch control unit gradually turns on the second transistor while the first transistor is turned on during a start-up period in which the step-up switching regulator transitions from a boost stop state to a boost operation state. The control circuit according to claim 2, wherein:

4. The synchronous rectification transistor, the first transistor, and the second transistor are P-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), according to any one of claims 1 to 3. Control circuit.

[5] A control circuit for a synchronous rectification step-down switching regulator,

A first terminal for outputting a switching voltage to an externally connected inductor, a second terminal for supplying an input voltage from the outside,

A switching transistor provided between the first terminal and the second terminal; a synchronous rectification transistor provided between the first terminal and the ground;

A first transistor provided between a knock gate of the switching transistor and the first terminal. And

A second transistor provided between the back gate of the switching transistor and the second terminal;

A control circuit comprising:

[6] The switch control unit turns off the first transistor and the second transistor in the step-down stop period of the step-down switching regulator driven by the control circuit, and turns off the first transistor and the second transistor in the step-down operation period. 6. The control circuit according to claim 5, wherein one transistor is turned off and the second transistor is turned on.

[7] The switch control unit gradually turns on the second transistor while the first transistor is turned off during the start-up period in which the step-down switching regulator transitions from the step-down stop state to the step-down operation state. The control circuit according to claim 6, wherein:

8. The control circuit according to claim 5, wherein the switching transistor, the first transistor, and the second transistor are P-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). .

[9] A switching regulator control circuit capable of switching between step-up mode and step-down mode,

A first switching transistor that functions as a switching transistor in the step-up mode and functions as a synchronous rectification transistor in the step-down mode;

A second switching transistor that functions as a synchronous rectification transistor in the step-up mode and functions as a switching transistor in the step-down mode;

A first transistor provided between a knock gate and a drain of the second switching transistor;

A second transistor provided between a knock gate and a source of the second switching transistor;

A control circuit comprising:

[10] The switching transistor, the synchronous rectification transistor, the first transistor, 10. The control circuit according to claim 1, wherein the second transistor and the switch control unit are integrated on a single semiconductor substrate.

[11] The control circuit according to any one of claims 1 to 3,

An inductor having one end connected to the first terminal of the control circuit and an input voltage applied to the other end;

An output capacitor having one end connected to the second terminal of the control circuit and the other end grounded;

A step-up switching regulator comprising: outputting a voltage at one end of the output capacitor.

[12] batteries,

The switching regulator according to claim 11, wherein the voltage of the battery is increased or decreased.

An electronic device comprising:

[13] an output capacitor with one end grounded;

An inductor having one end connected to the other end of the output capacitor;

The control circuit according to any one of claims 5 to 7, wherein the switching voltage is supplied to the other end of the inductor.

And a step-down switching regulator that outputs a voltage at the other end of the output capacitor.

[14] batteries,

The switching regulator according to claim 13, wherein the voltage of the battery is increased or decreased.

An electronic device comprising: